From f80a13d24aa95f7fa966a0bac1ecc5709d8f9bd2 Mon Sep 17 00:00:00 2001
From: Andreas Reich <r_andreas2@web.de>
Date: Tue, 28 Dec 2021 18:12:28 +0100
Subject: [PATCH] TextureInner::Surface can now be zero initialized

---
 wgpu-core/src/device/mod.rs | 24 +++++++++++++--------
 wgpu-core/src/present.rs    | 42 ++++++++++++++++++++++++++++++++++++-
 wgpu/examples/boids/main.rs |  4 +++-
 3 files changed, 59 insertions(+), 11 deletions(-)

diff --git a/wgpu-core/src/device/mod.rs b/wgpu-core/src/device/mod.rs
index 097eec3f2e..f2f86fbcda 100644
--- a/wgpu-core/src/device/mod.rs
+++ b/wgpu-core/src/device/mod.rs
@@ -3465,17 +3465,16 @@ impl<G: GlobalIdentityHandlerFactory> Global<G> {
 
         let last_submit_index = texture.life_guard.life_count();
 
+        let clear_views =
+            match std::mem::replace(&mut texture.clear_mode, resource::TextureClearMode::None) {
+                resource::TextureClearMode::BufferCopy => SmallVec::new(),
+                resource::TextureClearMode::RenderPass { clear_views, .. } => clear_views,
+                resource::TextureClearMode::None => SmallVec::new(),
+            };
+
         match texture.inner {
             resource::TextureInner::Native { ref mut raw } => {
                 let raw = raw.take().ok_or(resource::DestroyError::AlreadyDestroyed)?;
-                let clear_views = match std::mem::replace(
-                    &mut texture.clear_mode,
-                    resource::TextureClearMode::None,
-                ) {
-                    resource::TextureClearMode::BufferCopy => SmallVec::new(),
-                    resource::TextureClearMode::RenderPass { clear_views, .. } => clear_views,
-                    resource::TextureClearMode::None => SmallVec::new(),
-                };
                 let temp = queue::TempResource::Texture(raw, clear_views);
 
                 if device.pending_writes.dst_textures.contains(&texture_id) {
@@ -3487,7 +3486,14 @@ impl<G: GlobalIdentityHandlerFactory> Global<G> {
                         .schedule_resource_destruction(temp, last_submit_index);
                 }
             }
-            resource::TextureInner::Surface { .. } => {} //TODO
+            resource::TextureInner::Surface { .. } => {
+                for clear_view in clear_views {
+                    unsafe {
+                        device.raw.destroy_texture_view(clear_view);
+                    }
+                }
+                // TODO?
+            }
         }
 
         Ok(())
diff --git a/wgpu-core/src/present.rs b/wgpu-core/src/present.rs
index c13b8923cb..7421377ed7 100644
--- a/wgpu-core/src/present.rs
+++ b/wgpu-core/src/present.rs
@@ -9,6 +9,8 @@ When this texture is presented, we remove it from the device tracker as well as
 extract it from the hub.
 !*/
 
+use std::{borrow::Borrow, num::NonZeroU32};
+
 #[cfg(feature = "trace")]
 use crate::device::trace::Action;
 use crate::{
@@ -125,6 +127,31 @@ impl<G: GlobalIdentityHandlerFactory> Global<G> {
         let suf = A::get_surface_mut(surface);
         let (texture_id, status) = match unsafe { suf.raw.acquire_texture(FRAME_TIMEOUT_MS) } {
             Ok(Some(ast)) => {
+                let clear_view_desc = hal::TextureViewDescriptor {
+                    label: Some("clear texture view"),
+                    format: config.format,
+                    dimension: wgt::TextureViewDimension::D2,
+                    usage: hal::TextureUses::COLOR_TARGET,
+                    range: wgt::ImageSubresourceRange {
+                        aspect: wgt::TextureAspect::All,
+                        base_mip_level: 0,
+                        mip_level_count: NonZeroU32::new(1),
+                        base_array_layer: 0,
+                        array_layer_count: NonZeroU32::new(1),
+                    },
+                };
+                let mut clear_views = smallvec::SmallVec::new();
+                clear_views.push(
+                    unsafe {
+                        hal::Device::create_texture_view(
+                            &device.raw,
+                            &ast.texture.borrow(),
+                            &clear_view_desc,
+                        )
+                    }
+                    .map_err(DeviceError::from)?,
+                );
+
                 let present = surface.presentation.as_mut().unwrap();
                 let texture = resource::Texture {
                     inner: resource::TextureInner::Surface {
@@ -158,7 +185,10 @@ impl<G: GlobalIdentityHandlerFactory> Global<G> {
                         levels: 0..1,
                     },
                     life_guard: LifeGuard::new("<Surface>"),
-                    clear_mode: resource::TextureClearMode::None, // TODO: Shouldn't there be a view?
+                    clear_mode: resource::TextureClearMode::RenderPass {
+                        clear_views,
+                        is_color: true,
+                    },
                 };
 
                 let ref_count = texture.life_guard.add_ref();
@@ -240,6 +270,16 @@ impl<G: GlobalIdentityHandlerFactory> Global<G> {
 
             let (texture, _) = hub.textures.unregister(texture_id.value.0, &mut token);
             if let Some(texture) = texture {
+                if let resource::TextureClearMode::RenderPass { clear_views, .. } =
+                    texture.clear_mode
+                {
+                    for clear_view in clear_views {
+                        unsafe {
+                            hal::Device::destroy_texture_view(&device.raw, clear_view);
+                        }
+                    }
+                }
+
                 let suf = A::get_surface_mut(surface);
                 match texture.inner {
                     resource::TextureInner::Surface {
diff --git a/wgpu/examples/boids/main.rs b/wgpu/examples/boids/main.rs
index 919ba37074..043d4bc3f9 100644
--- a/wgpu/examples/boids/main.rs
+++ b/wgpu/examples/boids/main.rs
@@ -279,7 +279,9 @@ impl framework::Example for Example {
             view,
             resolve_target: None,
             ops: wgpu::Operations {
-                load: wgpu::LoadOp::Clear(wgpu::Color::BLACK),
+                // Not clearing here in order to test wgpu's zero texture initialization on a surface texture.
+                // Users should avoid loading uninitialized memory since this can cause additional overhead.
+                load: wgpu::LoadOp::Load,
                 store: true,
             },
         }];